PASADENA, CALIF. — When actor Ben McKenzie first came to Hollywood from his native Texas, he was surprised by what he found. “There’s no wizard behind the machine,” he says.

“It’s not like The Wizard of Oz, where there’s this big scary thing, but if you go in the back there’s just this guy. There’s no secret cabal of people that make decisions. It’s chaos! It’s every man and woman for himself — and go for it. And there’s not necessarily a, quote-unquote, right way to do it, particularly involving the press. Some people, the more press the better, the Paris Hiltons — then there are actors who do none and conscientiously avoid it. So it took a little while to find my bearings.”

Actually it took only a year, much less time than usual. McKenzie had been testing his luck in New York. Then an actor friend of his uncle’s, Ernie Sabella (the voice of Pumbaa in The Lion King), urged him to try Los Angeles.

“He was gracious enough to let me crash on his floor,” says McKenzie, ordering a burger and fries for lunch. “And a year and six days after I got to L.A. I landed the part on The O.C.”

McKenzie played Ryan Atwood, the troubled teen who’s taken in by a wealthy Orange County family in Fox’s enormous hit.

“It was a very odd experience because it was so quick, even for TV,” he says. “The entire casting process took about a week. And we were shooting a week or two later, and literally we wrapped on a Friday, and Monday or Tuesday the following week we were picked up. We shot in the summer and were on in August.”

McKenzie, who’d mostly done theater, had no clue about TV acting. “I barely knew what a mark was, what an eye line meant. All the technical stuff about acting on camera I knew very little. And to be one of the principals on a series like that where you’re working every day, all the time, was a lot. I look back on it now and look on it as basically my graduate school.”

If that was graduate school, he’s earned his Ph.D. with his latest role in NBC’s Southland, premiering Thursday. McKenzie plays a rookie cop who questions his choices his first day on the gritty job.

Produced by John Wells (ER), Southland is the most realistic police drama since Hill Street Blues. “Being on location in real L.A., that’s absolutely a significant part of the series,” he says. “We’re spending five or six days of every seven- or eight-day episode on location outside. We literally only shoot at the studio when we’re in the police department, which won’t be that much. My character will almost never be there, because we’re patrol officers, and we’re on the streets.”

The Austin-raised McKenzie attended the University of Virginia with an economics and foreign relations major. His dad’s a lawyer, his mom a poet. And acting wasn’t something to be considered seriously. But, bored with his classes, he wandered over to the drama department and found he loved acting.

His parents always supported him, even in defeat. He played football in high school and remembers it taught him to focus. “It’s quite violent, but there’s a lot of technique and strategy and a lot of discipline — being from Texas — almost militaristic discipline. And I really responded well to that. It made a lot of sense to me, because your adolescence is a tough time to decide who you are and what you want in your life and to act on your own for the first time.

“So I remember losing our last playoff game my senior year and realizing it was over and sitting in the kitchen talking about it with my father. ‘Are you OK?’ I said, ‘Yeah, it’s fine, fine, fine.’ Then he got up to hug me, and I started bawling. And that was a moment of realizing that that chapter had closed and there was a new chapter. I didn’t really focus on academics in high school. I did fine, but it was secondary to other things that were going on — football and girls. And it was a realization of a couple things: One, I needed to go on to new things, and two, I really did have that support of my family behind me. It was very comforting.”

Once he arrived in Los Angeles McKenzie desperately needed a car. “So I bought the cheapest car I could find in the Penny Saver, which was a 1986 Cadillac DeVille with 228,000 miles on it. No heat or A/C, and it overheated constantly. … For auditions I would have to leave three hours early, because if I got into traffic the thing would overheat, and I would pull over and basically wait for it to cool down. And I’d go again.

“It was a nightmare and basically a death trap. I bought myself a car when I got The O.C.”